Chapter 12: Selecting a Sample

Question 1

Sampling

Answer 1

• process of selecting “units” from a population of interest
• by studying the sample we may fairly generalize our results back to the population from which they were chosen

Question 2

Target Population

Answer 2

total group of individuals from which the sample might be drawn

Question 3

Generalizability

Answer 3

extent to which we can apply the findings of our research to the target population we are interested in

Question 4

Sampling Bias

Answer 4

• one of the problems that can occur when selecting the sample
• sampling has to reflect the characteristics of the target population

Question 5

Sampling Design/Strategy

Answer 5

the way you select the individuals that will be part of your sample

Question 6

Sampling Frame

Answer 6

a list identifying each individual in the study population

Question 7

Sample Statistics

Answer 7

findings based on the information obtained from your respondents (sample)

Question 8

In Quantitative Research

Answer 8

• quantify data and generalize results from a sample to the population of interest
• to measure the incidence of various views and opinions in a chosen sample
• sometimes followed by qualitative research which is used to explore some findings further
• usually large number of cases representing the population
• random selection

Question 9

In Qualitative Research

Answer 9

• gain understanding of underlying reasons and motivations
• provide insights into the setting of a problem, generating ideas and/or hypotheses for later quantitative research
• uncover prevalent trends in thought and opinion
• usually a small number of non-representative cases
• respondents are selected to fulfill a given quota

Question 10

Quantitative Research: Random Sampling Techniques

Answer 10

• simple random sampling
• systematic random sampling
• stratified random sampling (proportional, disproportional)
• cluster random sampling (one-stage, two-stage)

Question 11

Quantitative Research: Non-Random Sampling Techniques

Answer 11

• convenience sampling
• quota sampling
• purposive sampling
• snowball sampling

Question 12

Steps in Random Sampling

Answer 12

1. define population
2. choose sample size
3. list population
4. assign numbers to the units
5. find random numbers
6. select your sample

Question 13

Advantages of Random Sampling

Answer 13

• highly representative sample of the population
• reduced potential human bias in selection of the sample
• allows generalizations with external validity

Question 14

Disadvantages

Answer 14

• can only be carried out if the list of the population is available and complete
• challenging to access that list
• some populations are expensive and time consuming to contact

Question 15

Steps in Systematic Random Sampling

Answer 15

1. defining the population
2. choosing your sample size
3. listing the population
4. assigning numbers to the cases
5. calculating the sampling fraction
6. selecting the first unit
7. selecting your sample

Question 16

Advantages Systematic Random Assignment

Answer 16

• reduce the potential for human bias in the selection of cases
• allows statistical conclusions
• systematic procedure can be viewed as superior because it improves the potential for the units to be more evenly spread over the population

Question 17

Disadvantages

Answer 17

• only if a complete list of the population is available

- list has to have some kind of standardised arrangement

Question 18

Stratifies Random Sampling

Answer 18

when interested in particular strata (meaning groups) within the population

Question 19

Stratifies Random Sampling: Steps

Answer 19

1. defining the population
2. choosing the relevant stratification
3. listing the population
4. listing the population according the chosen stratification
5. choosing your sample size
6. calculating a proportionate stratification
7. using a simple random or systematic sample to select your sample

Question 20

Proportionate Stratified Random Sample

Answer 20

size of each strata is proportionate to the population size of the strata when looked across the entire population

Question 21

Disproportionate Stratified Random Sample

Answer 21

different strata do not have the same sampling fractions as each other

Question 22

Cluster Random Sampling

Answer 22

• researcher selects groups or clusters and then from each cluster the researcher selects the individual subjects by either simple random or systematic random sampling

Question 23

One-step Stage Cluster Sample

Answer 23

when the researcher includes all individuals from all the randomly selected clusters as sample

Question 24

Two-step Cluster Sample

Answer 24

when the researcher only selects a number of individuals from each cluster by using simple or systematics random sampling

Question 25

Non-Random Sampling: Convenience Sampling

Answer 25

subjects are selected because of their convenient accessibility and proximity to the researcher

Question 26

Non-Random Sampling: Quota Sampling

Answer 26

researcher selects people according to some fixed quota

Question 27

Non-Random Sampling: purposive sampling

Answer 27

sample is selected based on knowledge of a population and the purpose of the study

Question 28

Non-Random Sampling: Snowball Sampling

Answer 28

used by the researcher to identify potential subjects in studies where subjects are hard to locate

Question 29

The Calculation of Sample Size

Answer 29

- what level of confidence do you want to test your result - with what degree of accuracy do you wish to estimate the population parameters? - what is the estimated level or variation, with respect if the main variable you are studying in the population?

Question 30

Sampling in Qualitative Research

Answer 30

- aim to explore diversity, therefore concepts like sample size and sampling strategy are not essential when selecting a sample - non-probability (random) sampling designs can also be used in qualitative research with two main differences a. in qualitative research you do not have a predetermined sample b. in quantitative research you want to hace a random sample and in qualitative research you want to have the subjects that can provide you with the best information

Question 31

"Saturation Point" in Qualitative Research

Answer 31

- when in the process of collecting data you are or getting any new information ir it is negligible - the stage determined the sample size - it is a subjective concept. each researcher decides when she/he reached that point - more applicable to studies where you collect information a one-to-one basis